A Rectilinear Drive Mechanism Providing Counter-rotation. Speed Ratio Changes and Reciprocating Rectilinear Motion.

Field of the invention

The present invention relates to the field of mechanical transmissions traditionally using gear wheels, for example as used in road vehicles or marine applications, between the engine and the output drive shaft and is pertinent to reciprocating machines such as engines, expanders and compressors.

Background

Transmissions used in vehicle, marine or other mechanical applications where speed ratio changes are required traditionally use gear wheels. Meshing gear teeth have relatively small contact areas and, hence high contact pressures. The manufacture of the gear wheels, therefore, requires high strength, wear resistant materials and extreme dimensional accuracy. These factors contribute to relatively high cost of manufacture. Meshing gear wheels also usually act on a single plane such that the gears operate on different shafts which are positioned a distance apart which is dictated by the gear wheel diameters. A transmission using gears is, therefore, relatively bulky particularly in a direction perpendicular to the major axis of the input or output shaft. This invention discloses a mechanism that provides speed and torque ratio changes and reverse motion without the use of gear wheels, in transmission applications. The mechanism may also be used in reciprocating machines to provide counter rotating output shafts, as may be either required for aircraft or marine engines driving propellers, or reciprocating machines requiring primary balance, or engines or machines requiring both forward and reversing rotational outputs. The mechanism may also be used in reciprocating machines as a means of removing side thrust from a reciprocating piston. Other applications may be in compressors and expanders, or combinations of compressors and expanders, as may be used in heat pumps, refrigerators or external combustion engines such as steam engines and Stirling cycle engines.

To simplify the description of the invention, the following terms are defined in the context of this invention and are also generally used in relation to machines.

Definitions & Terminology hi the context of this invention, the following terms are used.

A speed or torque ratio refers to a change of speed or torque achieved when energy is transferred through a machine that is designed to multiply or divide the input speed or torque.

A journal is a solid of revolution which is used as the male portion of a bearing, the journal frequently being part of a rotating shaft, such as a crankshaft.

A crankshaft is a shaft having a major axis of rotation, with some first journal elements of the shaft aligned along that axis of rotation, and having some second journal elements, sometimes known as crankpins, that are rigidly fixed by radial arms to said first elements, these second elements being offset from and parallel to the major axis of rotation of the shaft.

A yoke is a substantially rigid link that joins two other parts, usually having some clearance with each of these other two parts so that there is some degree of rotational freedom between the link and the two parts.

"Ground" signifies the part of the engine or mechanism that is stationary and connected mechanically or by gravity to earth.

Prime rotational speed is the speed of rotation of the input shaft of the mechanism.

An Oldham Coupling consists of three parallel mounted discs, the centre disc being free to move laterally and the outer discs being fixed to the drive input and output. The outer discs have slots or lugs, arranged orthogonally, which engage slideably with mating lugs or slots in the central disc. The central disc transfers drive between the outer discs while moving laterally as well as rotating.

A multicrank device performs the same function as the Oldham Coupling. It consists of two plates which have at least three cranks rotatably mounted between them. The plates are mounted on the input and output shafts. The cranks are all on parallel axes which are orthogonal to the planes of the plates and allow lateral movement of the centres of the plates as well as rotation of the plates.

A centering mechanism is a coupling which enables a cyclically variable rotary motion to be transferred from one axis to another substantially parallel axis. Examples of these mechanisms include oldham couplings and multicranks.

A rectilinear drive mechanism is an assembly comprising a crankshaft fitted with paired discs (usually cylindrically shaped) which can rotate with clearance about the crankpin of the crankshaft, each disc of the pair being guided and constrained with clearance by at least one linear rail and the rail(s) of each disc being orthogonal to each other. For clarity, further description of rectilinear drive mechanisms is given with reference to diagrams, in the following sections.

Paired discs, sometimes referred to as paired eccentrics, are a component of a rectilinear drive mechanism which consist of two eccentric discs rigidly fixed together and which are able to rotate (as one body) about a point which is central between the two centres of the discs. In one form of rectilinear drive mechanism described below, the discs are of a small diameter and are in the form of pins which are joined by a rigid bar. The assembly of the bar and the two pins thus forms paired discs.

A reciprocating machine is a mechanism in which at least one component oscillates (travels along a single line with periodically reversing direction of motion) and which has a link between that reciprocating motion and the rotational motion of at least one shaft.

An input shaft is a rotating drive conducting torque, or turning motion, into a machine. An output shaft is a rotating drive conducting torque, or turning motion, from a machine.

A linear guide is a substantially straight (but not necessarily flat) component fixed to ground and which has a groove or straight edge which engages with a moving component such that the moving component is constrained to move with linear motion. An example of a linear guide could be a cylinder in an engine or compressor.

Fracture splitting is a production technique involving the creation of an accurately matching joint with self locating surfaces between two components by breaking one component into two pieces in a controlled manner. The surfaces so formed can be described as fracture split surfaces.

A crosshead arrangement in a reciprocating machine such as an engine or compressor is one in which the active piston is supported on a carrier piston or slider through which all, or most, of the side loads are transmitted. This has the principal advantage that little lubrication is required on the side surfaces of the active piston.

Prior Art

Conventional stepped transmissions using gear wheels are well known and numerous. In the automotive field, for example, patent number US 2006/0174722 Al discloses a transmission (gearbox) using two parallel shafts onto which gear wheels are mounted and can be selectively engaged to give ratio changes. Transmissions of this type typically provide a reversing function and five forward ratios. There are also many examples of gearless transmissions using a variety of mechanisms. One example is disclosed in patent number US5443428. The current invention discloses a transmission capable of providing a reversing function and a plurality of forward ratios but with advantages of reduced complexity, lower cost manufacture and increased compactness. The invention employs a mechanism known as a rectilinear drive mechanism.

Some of the embodiments which will be described are suitable for use in reciprocating machines such as engines, expanders and compressors. Rectilinear drive mechanisms exist in the field of engines and an example of such an application can be found in European Patent number 0 493 135 Al. A core component of the rectilinear drive mechanism is the paired discs which rotates in a direction counter to the direction of the input or output shaft. In known applications of the rectilinear drive mechanism, such as European Patent number 0 493 135 Al, there is no mechanical link to the paired discs so that the reverse rotation is not utilized. The present invention provides a means of connecting the rotation of the paired discs to a shaft such that its rotation can be utilized.

The present invention thus develops the rectilinear drive mechanism such that it provides additional benefits in transmissions and in reciprocating machines and combinations thereof.

Summary of the invention

The broadest aspect of the first embodiment of the invention comprises a transmission with an input shaft, an output shaft and intermediate components which include at least one rectilinear drive mechanism.

The broadest aspect of another embodiment of the invention comprises a reciprocating machine employing a rectilinear drive mechanism including paired discs mounted on a crank pin in which there is a connection between said paired discs and at least one shaft such that the rotation of said paired discs about said crank pin may be translated into rotation of said shaft.

The broadest aspect of a further embodiment of the invention comprises a reciprocating machine containing at least one rectilinear drive mechanism which includes a first carrier and a second carrier and in which only the first carrier is constrained to move with rectilinear motion using a linear guide while the second carrier moves with rectilinear motion but is not constrained by any linear guide.

Brief Description of the Figures

Figure 1 is an isometric view of a simplified link diagram of a rectilinear drive mechanism with the crank in a first position.

Figure 2a is a plan view of the simplified link diagram of a rectilinear drive mechanism, shown with the elements in a first position.

Figure 2b is a plan view of the simplified link diagram of a rectilinear drive mechanism, shown with the elements in a second position.

Figure 3 is an isometric view of a further example of a rectilinear drive mechanism. Figure 4 is an isometric view of one embodiment of the invention.

Figure 4a shows a schematic view of a transmission containing two rectilinear drive mechanisms in series.

Figure 5 is an exploded isometric view of an embodiment of the invention in the form of a reciprocating piston machine with contra-rotating shafts.

Figure 6 is an exploded isometric view of another embodiment which can be used to provide rectilinear motion with constraint of only one of the driving plates.

Figure 7 is an isometric assembly of a gear drive which may be used in conjunction with the mechanism shown in Fig.6.

Figure 8 shows an arrangement of a paired disc. Figure 9 shows an arrangement of a carrier.

Figure 10 shows an arrangement of a carrier, piston rod, piston, assembly for use in a reciprocating machine.

Figure 11 shows a further arrangement of a carrier, piston rod, piston, assembly for use in a reciprocating machine.

These figures will now be described to clarify the features of the invention. Detailed Description of the Preferred Embodiments

With reference to Fig.l, which is a skeletal model to show the principles of the rectilinear drive mechanism, there is a first axis 1 along which lies the main journal 2, which may be considered as an input shaft, which is rigidly attached to a crank arm 3 which in turn is rigidly connected to a crankpin 4 which carries, with clearance, a rigid body 7 to which are attached 2 pin joints 5 (not visible in Fig.l) and 6, each with its major axis parallel to the major crankpin axis and each of these pin axes being at a distance X from the major axis of the crankpin and each pin 5 and 6 being rotatably connected to sliding blocks 10 and 11 respectively. The offset between first axis 1 and the major axis of crankpin 4 is also, preferably, equal to X. Blocks 10 and 11 engage with corresponding channels 8 and 9 which are rectilinear and are located in fixture plate 12. In this skeletal model, each pin 5 and 6 represents the centre of an eccentric disc, the two discs being rigidly joined by the rigid body 7 and each pin 5 and 6 being constrained to move in the channels 8 and 9 respectively. A line joining each centre of the pins 5 and 6 passes through the centre of the crankpin 4. On turning the input shaft or crank arm 3 in an anti-clockwise direction (as viewed from above), slider block 10 will move towards point A, whilst slider block 11 will move towards point D. When the crank arm lies parallel to channel 8, slider block 10 will be at its closest to point A whilst slider block 11 will be at the crossing point of channels 8 and 9.

On further anti-clockwise rotation of crank arm 3, slider block 10 moves back towards point C whilst slider block 11 continues from the crossing point of the channels towards point D. It can be seen that while crank arm 3 moves in an anti-clockwise direction the central axis of rigid body 7 also moves in an anti-clockwise direction but rigid body 7 rotates in a clockwise direction about its central axis. The assembly 5-6-7 thus rotates in an opposite direction to the crank arm, though at the same rotational speed. The rectilinear drive mechanism therefore provides a reversing capability, although, as will be explained further, the axis of rotation of the reversing assembly 5-6-7, which is the crankpin axis, needs to be transposed to the main axis 1 for most practical applications.

In the above description, fixture plate 12 is stationary and crank arm 3 is rotating. It is important now to consider the case where crank arm 3 is held stationary and fixture plate 12 is rotated about axis 1. Figures 2a and 2b, show the relative movements of the assembly 5-6-7 in response to the bodily rotation of fixture plate 12 and channels 8 and 9. In Figure 2b fixture plate 12 has moved 90° in an anti-clockwise direction in relation to the position shown in Figure 2a. Crank arm 3 has remained stationary but rigid body 7 has moved 180° in an anti-clockwise direction. It can thus be seen that 90° rotation of fixture plate 12 results in 180° rotation of the assembly 5-6-7. In this case, the rectilinear drive mechanism provides a 2:1 speed multiplication of the assembly 5-6-7 relative to the fixture rotation.

As noted previously, with reference to Figsl, 2a and 2b, the assembly 5-6-7 represents the paired discs of the rectilinear drive mechanism, the pins 5 and 6 representing the centres of a pair of discs that are rigidly joined and constrained to move in the rectilinear channels. These paired discs can be part of an output shaft. The following description, therefore, covers what is, in effect, the same mechanism in a different form and one which is more likely to be used in a practical application with conventional input and output shafts.

Figure 3 shows a rectilinear drive mechanism in a similar form to that which can be employed in engines to produce rectilinear thrust for piston actuation and pure sinusoidal piston motion. An example of this is shown in European Patent number 0 493 135 Al. With reference to Figure 3, crank 20, which could be part of an input shaft, rotating about axis 21, is rigidly attached to crankpin 22 onto which is rotatably mounted paired discs 23. Crankpin 22 is shown split into two separate sections, for clarity. Paired discs 23 is one component consisting substantially of two discs, disc 31 with central axis 29 and disc 32 with central axis 30. Central axes 29 and 30 are preferably both the same distance from axis 33 as axis 33 is from axis 21. The centre of disc 31 is constrained to move in direction 34 by means of guides 26 and 27. The centre of disc 32 is constrained to move in direction 35 by means of guides 36 and 37. Axis 35 is substantially orthogonal to axis 34. Guides 26, 27, 36, and 37 are connected together in the form of a frame and mounted onto fixture plate 38. For clarity, the frame is shown separated from fixture plate 38. Paired discs 23, which could be part of an output shaft, is the equivalent of assembly 5-6- 7 in Figures 1 to 2b. When input shaft or crank 20 is rotated, paired discs 23, or output shaft, rotates in the opposite direction about axis 33. As with the example described with reference to Figures 1 to 2b, the rate of rotation of paired discs 23 is equal to the rate of rotation of crank 20.

The following description explains how, in the first embodiment of the invention, it is possible to harness the characteristics of a rectilinear drive mechanism to provide reverse rotation and variable speed ratios in a transmission. Figure 4 shows the same components that were described with reference to Figure 3 but with some additional components and features that will be described. In this embodiment, fixture plate 38 is mounted on a shaft (not shown) which is an extension of crank 20 (see Figure 3) and fixture plate 38 is able to rotate on the shaft, about axis 21. The rotation may be selectively prevented by engaging a clutch (not shown) which fixes fixture plate 38 in

relation to the casing (not shown) of the mechanism. Paired discs 23 are shown separated from crankpin 22, for clarity. In practice these components would be assembled as was shown with reference to Figure 3. As was described previously (with reference to Figure 3), when crank 20 is rotated, paired discs 23 rotates in the opposite direction about axis 33. Crank 20 is connected to the input shaft (not shown) of the transmission. Since axis 33 is also rotating about axis 21 it is necessary to use a centering mechanism in order that the counter rotation of paired discs 23 can be converted into a useful output to a shaft with a fixed axis. One such centering mechanism may be an Oldham Coupling which is a well known mechanism. Another suitable device (multicrank) is shown in Figure 4. Plates 45 and 46 are joined by preferably 4 cranks, 47, 48, 49 and 50. Plate 46 is fixed to disc 32 and rotatably mounted on crankpin 22 which is located in hole 51. Cranks 47, 48, 49 and 50 are rotatably mounted in holes 53, 54, 52 and 55 in plate 45. Crank 20 (not visible in Figure 4 but shown in Figure 3) protrudes, with clearance through hole 56 in plate 45. When fixture plate 38 is fixed and crank 20 is rotated, plate 45 rotates at the same speed but in the opposite direction. This arrangement, therefore, represents a selectable counter rotation or reversing mechanism. The selection is made by locking fixture plate 38 in position. Plate 45 may be fitted with a suitable drive take off (not shown) connected to an output shaft (not shown) from the transmission. Plate 45 may also be locked in position by engaging a clutch (not shown) which fixes plate 45 in relation to the casing (not shown) of the mechanism. When plate 45 is locked in position and fixture plate 38 is unlocked, rotation of crank 20 causes rotation of fixture plate 38 in the same direction but at half the speed. This arrangement, therefore, represents a selectable ratio change mechanism. The selection is made by locking plate 45 in position and unlocking fixture plate 38. Fixture plate 38 may be fitted with a suitable drive take off (not shown) connected to an output shaft (not shown) from the transmission. If plate 45 and fixture plate 38 are both unlocked and crank 20 is rotated then fixture plate 38 rotates in the same direction at the same speed (direct drive). This is also, therefore, a selectable function of the transmission.

In another embodiment, the multicrank assembly 45 - 50 may be fitted to the other side of the paired discs 23, i.e. to disc 31, to enable the output drive to be taken from the right hand side of the mechanism shown in Figure 4.

The embodiment shown in Figure 4 represents a transmission providing selectable reversing and single ratio change functions. In other embodiments two or more such systems may be connected in series with additional clutches so that further ratio changes are possible. Figure 4a, for example, shows, schematically, a transmission with two such systems in series. With this arrangement it is possible to select two reversing functions (two ratios), a direct drive output, a two to one ratio output and a four to one ratio output.

Referring to Figure 4a, centering mechanism 143, paired discs 144 and fixture plate 145 represent substantially the same mechanism as described with reference to Figure 4. Similarly, second centering mechanism 151, second paired disc 152 and second fixture plate 153 represent substantially the same mechanism as described with reference to Figure 4. Input shaft 140 passes through bearing 141 and is connected to a crankshaft (not shown) which rotates within paired disc 144 and fixture plate 145 and is connected to

intermediate output shaft 158. Centering mechanism 143 is connected to reverse output shaft 146 via sleeve 147. Reverse output shaft 146 and intermediate output shaft 158 can be selectively connected to secondary input shaft 150 by means of clutch 149. Secondary input shaft 150 passes through centering mechanism 151 and is connected to a crankshaft (not shown) which rotates within paired disc 152 and fixture plate 153. Centering mechanism 143 can be selectively locked to outer casing 142 using clutch 148. Centering mechanism 151 can be selectively locked to outer casing 142 using clutch 156. Output shaft 154 passes through bearing 155 and is connected to fixture plate 153. With this arrangement output speeds are selected as follows;

If clutches 148, 156 and 157 are unlocked and clutch 149 is connected to intermediate output shaft 158 the drive is direct with the output speed being equal to the input speed and in the same direction of rotation.

If the above conditions are maintained except that clutch 148 is locked then the output speed is half the input speed and in the same direction of rotation. If, in addition, clutch 156 is locked, then the output speed is one quarter of the input speed and in the same direction of rotation.

If clutches 148, 156 and 157 are unlocked and clutch 149 is connected to reverse output shaft 146 then the output speed is equal to the input speed but in the reverse direction. If these conditions are maintained except that clutch 148 is locked then the output speed is half the input speed but in the reverse direction. If, in addition, clutch 156 is locked, then the output speed is one quarter of the input speed and in the reverse direction. In any of the above conditions input shaft 140 may be used as an output shaft and output shaft 154 may be used as an input shaft.

In another embodiment of the invention the guides are formed by two pairs of stepped faces in the yoke. The first pair of stepped faces is in the plane of disc 31 and the second pair of stepped faces is in the plane of disc 32 and is orthogonal to the first pair of stepped faces. The stepped faces may be formed, for example, as a single sintered part or as a single stamped part.

In another embodiment the yoke may be made in two parts, the first part containing the first pair of stepped faces and the second part containing the second pair of stepped faces, both parts being rigidly joined. These two parts may, optionally, be sintered and may include interlocking features to enable them to be fixed together. Alternatively the two parts may be stamped and may include interlocking features to enable them to be fixed together.

Plain or rolling element bearings may be used for any of the cylindrical bearings on the crankpins, main journals, paired discs. The plain bearings may be oil or grease lubricated.

There are many possible applications of the above transmission, for example, it may be fitted to an engine crankshaft to provide a speed reduction for driving the valve train or

for a speed reduction to a propeller as might be used in a marine or aviation application. Similarly,, when mounted on the front of a crankshaft the mechanism can be used to provide selectively variable ratio drives to the engine auxiliaries via belts, chains or gears. In these engine applications speed ratios or a reversing function are selectable by means of at least one clutch.

A variety of types of clutches may be used in the embodiments described, including frictional plate, frictional cone and dog clutches.

A characteristic of the rectilinear drive mechanism is that it readily provides reciprocating motion in two orthogonal directions. In Figure 1, for example, it can be seen that sliding blocks 10 and 11 move in a reciprocating manner within channels 8 and 9 respectively. Similarly, in Figure 3, the central axis 29 of disc 31 and the central axis 30 of disc 32 move with reciprocating motion with the directions of motion substantially orthogonal to each other. In the above embodiments of the invention the reciprocating motion is a byproduct of the mechanism. In some embodiments of the invention, as will be described, the device may be configured to harness the link between the reciprocation motion and the rotational motion of the input or output shafts.

Figure 5 shows an embodiment of the invention in which the mechanism links counter rotation of two concentric shafts with reciprocating motion in two orthogonal directions, in this case arranged in a cruciform pattern. For clarity the figure shows the components in an exploded isometric view. Referring to the figure, paired discs 60 are attached such that they form a single rotatable component. Crank 62 has pin 63 located in a central hole (not shown) through paired disc 60 which is rotatably mounted within carriers 64 and 65. Each of the carriers 64 and 65 moves in a reciprocating manner in relation to the fixed casing (not shown) of the mechanism. Carrier 64 is guided by the surfaces within slot 75 within fixture plate 76 and carrier 65 is guided by surfaces 58 and 59 within fixture plate 76. Shafts 61 and 77 are rigidly connected to crank 62. As shaft 77 rotates, crankpin 63 also rotates in the same direction causing paired disc 60 to rotate in the opposite direction as has been shown in the earlier embodiments. The centre of that rotation is coincident with the centre of pin 63 which moves in a circular path around the central axis 57 of shafts 61 and 77. The orbital rotation of paired disc 60 is translated into rotation about axis 57 by means of a centering mechanism. The type of centering mechanism shown in the figure, as an example, is the multicrank mechanism as described in connection with previous embodiments. Paired disc 60 is rigidly connected to plate 70 which is rotatably connected to plate 71 by means of, preferably, four cranks (only 3 shown 72, 73, 74). The cranks 72, 73, 74 (including the one not shown) are rotatably located within holes 66 to 69. Plate 71, therefore, rotates in a direction opposite to the rotation of shaft 77. Plate 71 is rigidly connected to hollow shaft 76 which, therefore, also rotates in a direction opposite to that of shaft 77. Shaft 61 runs through the centre of shaft 76. For a clockwise rotation of shaft 77, therefore, shaft 61 rotates in a clockwise direction at the same speed and hollow shaft 76 rotates in an anti-clockwise direction at the same speed. Carriers 64 and 65 also move with perfect sinusoidal reciprocating motion with one complete cycle for every complete rotation of shafts 61 and 77. If shaft 77 rotates in an anti-clockwise direction then shaft 61 rotates in an anti-clockwise direction at the same speed and hollow

shaft 76 rotates in a clockwise direction at the same speed. In the arrangement shown. each of carriers 64 and 65 is connected to two pistons. Carrier 64 is connected to pistons 79 and 80 via piston rods 791 and 801 respectively. Carrier 65 is connected to pistons 78 and 81 via piston rods 781 and 811 respectively. The mechanism as described may be used in piston engine, expander or compressor applications. In such applications, carriers 64 and 65 may be rigidly connected to pistons which run in cylinder bores (not shown). Piston rods 781, 791, 801 and 811 may run through bearings which absorb side load due to the torque transmitted through the system. In this case it may not be necessary for carriers 64 and 65 to be guided. The piston to cylinder bore interface would, therefore, be subject to substantially zero side load which confers lubrication advantages. The drive for motion of the mechanism, in the engine and expander embodiments, comes from the pistons which reciprocate causing rotation of shaft 61 and rotation of hollow shaft 76 in the opposite direction. In one application, the mechanism may be used as part of an aircraft engine and shafts 61 and 76 may be attached to propellers which have opposite handed pitch. In this embodiment the engine drives the propellers so that they spin in opposite directions without the need for a gear mechanism. Alternatively, in another embodiment, shaft 77 may be the output shaft from the engine while shafts 76 and 61 are connected to counter-rotating flywheels. In another embodiment, the carrier 64 may be guided in a first linear direction, and the carrier 65 may be guided in a second linear direction, orthogonal to the first direction. In another embodiment, the orthogonal guides for carriers 64 and 65 may be part of the casing that contains the mechanism, or attached to said casing.

Figures 6 and 7 show another embodiment of the invention which forms part of a reciprocating machine in which it is required to remove any side thrust from one of the reciprocating members. In Figure 6 shaft 111 is connected to crank 112 which has a crankpin 82 located in hole 83 through paired discs 86 comprising two discs 84 and 85 rigidly attached together. Disc 84 is rotatably located in carrier 87 and disc 85 is rotatably located in carrier 88. Carriers 87 and 88 are rotatably connected by, preferably, four cranks 89 - 92. Carrier 88 is guided to move in a straight line by a linear guide. The arrangement shown (Figure 7 only), as an example, is that two of the parallel sides of carrier 88 are guided by surfaces 100 and 101 of support 102. Shaft 104 is connected to crank 112 and protrudes through a hole (not shown) in support 102 in which it is able to rotate and is, preferably, supported in a bearing, not shown. Disc 84 is rigidly connected to bar 93 which is shdeably located in slot 94 in ring 95. Bar 97 is slideably located in slot 96 in ring 95. Bar 97 is rigidly fixed to hollow shaft 98. Hollow shaft 98 and shaft 111 are not directly connected but they share the same central axis 99. Shaft 111 is stepped and has a smaller diameter section which passes through the centre of hollow shaft 98. Hollow shaft 98 and shaft 111 are connected via, preferable, a set of gears which ensure that the shafts rotate at the same speed but in opposite directions, hi the arrangement shown in Figure 7, as an example, gears 105 and 106 are rigidly mounted on lay shaft 107, offset from the axis of the main drive axis of shafts 111 and 98. Gear 108 is rigidly connected to hollow shaft 98 and gear 109 is rigidly connected to shaft 111. Gear 109 also interacts with idler gear 110 which interacts with gear 106 via gear 114, as gear 110 is rigidly joined to gear 114. If shaft 111 rotates in a clockwise direction, gear 109 transfers this rotation via idler gear 110, located on layshaft 113, to gear 106. Gear

106 causes layshaft 107 and gear 105 also to rotate in a clockwise direction. Gear 105 interacts with gear 108 which, therefore, rotates in an anti-clockwise direction causing hollow shaft 98 to rotate in an anti-clockwise direction. Similarly, if shaft 111 rotates in an anti-clockwise direction, shaft 98 rotates in a clockwise direction.

The mechanism shown in Figure 5, therefore, provides a rectilineal" drive mechanism including paired discs (60-66) mounted on crank pin (63) in which there is a connection between the paired discs and at least one shaft (76-77) such that the rotation of the paired discs about the crank pin may be translated into rotation of the shaft. Preferably the mechanism would include two concentric shafts rotating in opposite directions. The connection between the paired discs (60-66) and shaft (76-77) is made via a centering mechanism which is preferably of the multi-crank or Oldham Coupling type.

Referring to Figures 6 and 7, clockwise rotation of shaft 111 and crank 112 causes the centre of (which is coincident with the axis of pin 82) to move in a circular path in a clockwise direction. Carrier 88 is constrained by surfaces 100 and 101 to move in a straight line. This prevents the whole carrier and paired discs assembly from rotating with crank 82. Carrier 88, therefore, reciprocates in a direction parallel with surfaces 100 and 101. Since carrier 87 and carrier 88 are joined by cranks 89 -92, there can be no angular motion between the two carriers. That is to say that in the case of square carriers, as shown, the equivalent sides of the carriers always remain parallel. Clockwise rotation of shaft 111 causes hollow shaft 98 and bar 97 to rotate in an anti-clockwise direction, due to the effect of the gear assembly 105 - 113. That in turn causes ring 95, bar 93 and paired discs 84 to rotate in an anti-clockwise direction. The rotation of bar 97 is about axis 99 whereas the rotation of paired discs 84 is about the centre of pin 82 which moves in a circular path around axis 99. However, the different centres of rotation are accommodated by the sliding of bars 93 and 97 within slots 94 and 96, respectively, in ring 95. The combined effects of the anti-clockwise rotation of paired discs 84, the reciprocating motion of carrier 88 and the rotation of cranks 89 - 92 is to cause carrier 87 to move with a reciprocating motion orthogonal to that of carrier 88.

Figure 8 shows a further embodiment of the invention which may be used in combination with other embodiments described. The figure shows paired disc 120 comprising two components 121 and 122 rigidly fixed together along joint 123. Paired disc 120 may, for example, take the place of paired disc 86 shown in Figure 7. Referring again to Figure 8, joint 123 may pass through the centres of discs 124 and 125 but this is not essential. The axis 129 of joint 123 must, however, pass substantially through the centre of hole 128. The two sections 121 and 122 of paired disc 120 may be fixed together with at least two bolts, setscrews or similar fixings (not shown) along axes such as 126 and 127. The bolts or setscrews are recessed so that they do not protrude outside the peripheries of discs 124 and 125. Joint 123 may be comprised of machined, substantially flat surfaces or it may be a fracture split surface. The purpose of joint 123 is to allow ease of assembly of the paired disc onto a crankshaft (not shown) when the crankshaft is a single component.

Figure 9 shows a further embodiment of the invention which may be used in combination with other embodiments described. The figure shows carrier 130 which may, for

example, take the place of carriers 64 or 65 in Figure 5. Referring again to Figure 9, carrier 130 is comprised of two components 131 and 132 rigidly fixed together along joint 135, the axis 129 of which passes substantially through the centre of hole 136. The two sections 131 and 132 of carrier 130 may be fixed together with at least two bolts setscrews or similar fixings (not shown) along axes such as 133 and 134. Joint 135 may be comprised of machined, substantially flat surfaces or it may be a fracture split surface. The purpose of joint 135 is to allow ease of assembly of the carrier onto a paired disc (not shown) when the crankshaft (not shown) on which the paired disc is mounted is a single component.

Figures 10 and 11 show further embodiments of the invention which are applied to reciprocating machines with pistons. In these embodiments the piston is supported on a carrier in a crosshead arrangement. These embodiments allow for a degree of lateral movement of the piston so that it can provide an effective seal with the cylinder wall (not shown) and run freely in the cylinder even with minor dimensional inaccuracies in the production process. Figure 10 shows one carrier 170 which represents a part of a rectilinear drive mechanism the rest of which is not shown. The carrier is similar, for example, to carriers 64 and 65 shown in Figure 5. Referring again to Figure 10, carrier 170 is connected to piston 172 by means of piston rod 171. Hole 176 contains a disc (not shown) and the principal axis of the hole passes through centre 177. Piston 172 is mounted on piston rod 171 by means of gudgeon pin 174 the axis 175 of which is orthogonal to the wall of the cylinder (not shown) and orthogonal to the principal axis of hole 176. This orientation of gudgeon pin 174 allows for minor movement along axis 175. Minor movement in the orthogonal direction (that is the direction of the principal axis of hole 176) is also provided due to end float in the mounting of carrier 170 on the disc (not shown). In the example shown, guiding of the carrier 170 piston rod 171 and piston 172 assembly is effected by means of guide 173 which may, optionally, also contain a seal (not shown) allowing lubricating oil to be substantially excluded from the cylinder (not shown) in which piston 172 is slideably located. Piston rod 171 is preferably cylindrical in shape and guide 173 is preferably also cylindrical and in sliding contact with piston rod 171.

Figure 11 shows a similar arrangement of guide 170, piston rod 171 and piston 172 but in this embodiment guiding is effected by means of guide surfaces 180 and 181 which are in sliding contact with carrier 170. In both Figures 10 and 11 piston location is shown by means of gudgeon pin 174. Other means of attachment are possible. For example, piston 172 may be rigidly attached to piston rod 171 and piston rod 171 may be slideably connected to carrier 170 by a joint similar to a dovetail joint which is well known in the field of carpentry. The axis of the joint must be in a direction which allows minor movement of piston rod 171 in a direction orthogonal to the wall of the cylinder (not shown) and orthogonal to the principal axis of hole 176.

The embodiments shown in Figures 6 and 7 provide a reciprocating machine containing at least one rectilinear drive mechanism which includes first carrier (87) and second carrier (88) and in which only first carrier (88) is constrained to move with rectilinear

motion using linear guide (100 - 102) while second carrier (87) moves with rectilinear motion but is not constrained by any linear guide.

These same embodiments preferably include at least one rectilinear drive mechanism and at least two centering mechanisms. These embodiments also include two concentric shafts (111 & 98) which are caused to counter-rotate preferably by engagement with a set of gears (105, 106, 108, 109, 110, 113, 114).

Those embodiments of the invention, as described with reference to Figs.5-7, which may be used for reciprocating machines with pistons, can be arranged such that at least two pistons move orthogonally to each other with sinusoidal motion, and therefore may be phased relative to each other with a rotational phase angle of 90°.

These same machines may have at least four pistons (78-91, Fig.5) moving relative to each other with a rotational phase angle of 90°.

Ih another embodiment of the invention, these reciprocating machines may have pistons which are double acting, which enables both sides of the piston to be used for moving working fluids.

In another embodiment of the invention, these reciprocating machines may have pistons which have double diameters, each diameter of the piston engaging with a corresponding cylinder, therefore enabling each diameter of the piston to handle a separate volume of working fluid.

In a further embodiment of the invention, the fluid motion from reciprocating pistons may be interconnected via conduits from one piston volume to another piston volume.

In one embodiment of the invention, the fluid motion from reciprocating pistons may be transferred from one side of the piston to the other side of the same piston via at least one conduit.

Embodiments of these inventions may be used in reciprocating machines as part of: internal combustion engines Rankine cycle expanders compressors external combustion engines, such as the Stirling cycle engine and Erikson cycle engines and compressors in refrigeration and liquifaction machines.